A conventional digital light processing (DLP) projector includes an illumination system, a digital micro-mirror device (DMD) and a projection lens. The illumination system is used to provide an illumination beam, the digital micro-mirror device is used to convert the illumination beam into an image beam, and the projection lens is used to project the image beam onto a screen to form an image screen on the screen. In addition, with the development of illumination technology, most of the aforementioned projectors have employed laser sources as the light source of the illumination system, wherein the laser source can be a laser diode (LD).
FIG. 1 is a schematic view of a conventional illumination system employing a laser source. Referring to FIG. 1. In the illumination system 100, the laser source module 110 can emit a blue beam 112. The blue beam 112 is irradiated to the phosphor wheel 140 after passing through the collimating element 122, the dichroic mirror 130 and the lenses 123, 124 sequentially. The phosphor wheel 140 can be rotated and has a reflective portion, a green phosphor region, a yellow phosphor region and a transmissive region or an opening region (these elements of the phosphor wheel 140 are not shown), and the green phosphor region and the yellow phosphor region both are formed on the reflective portion.
When the blue beam 112 is individually irradiated to the green phosphor region and the yellow phosphor region, the green beam 113 and the yellow beam 114 are excited from the green phosphor region and the yellow phosphor region respectively, and the reflective portion reflects the green light beam 113 and the yellow light beam 114 to the dichroic mirror 130. The green light beam 113 and the yellow light beam 114 are reflected by the dichroic mirror 130, pass through the lens 125, and are irradiated to the rotatable color wheel 150. The opening region of the phosphor wheel 140 may allow the blue beam 112 to penetrate. After passing through the opening region, the blue beam 112 passes through the lenses 126, 127, the reflective portions 161, 162, the lens 128, the reflective portion 163, the lens 129, the dichroic mirror 130 and the lens 125. Thereafter, the blue beam 112 is irradiated to the color wheel 150.
The color wheel 150 has a red filter region, a green filter region, a transparent region and a diffusion region. The yellow phosphor region corresponds to the red filter region and the transparent region, the green phosphor region corresponds to the green filter region, and the opening region corresponds to the diffusion region. The color wheel 150 and the phosphor wheel 140 are rotatably engaged with each other so that the green beam 113 is irradiated to the green filter region, the yellow beam 114 is irradiated to the red filter region and the transparent region, and the blue beam 112 is irradiated on the diffusion region. The color light beams filtered by the color wheel 150 are a blue beam, a green beam and a red beam for forming a color image and a yellow beam for increasing the luminance. Each of the color light beams enters the optical integration rod 170.
However, from the above description, it is known that the conventional illumination system 100 requires many optical elements (e.g., a plurality of lenses 123 to 128) and the optical layout of the illumination system 100 is complicated, thus, the conventional illumination system 100 has some disadvantages such as high cost, large volume and poor optical efficiency.
The information disclosed in this “BACKGROUND OF THE INVENTION” section is only for enhancement understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Furthermore, the information disclosed in this “BACKGROUND OF THE INVENTION” section does not mean that one or more problems to be solved by one or more embodiments of the invention were acknowledged by a person of ordinary skill in the art.